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MEM(4) Device Drivers Manual (vax) MEM(4)

mem, kmemmemory files

The special file /dev/mem is an interface to the physical memory of the computer. Byte offsets in this file are interpreted as physical memory addresses. Reading and writing this file is equivalent to reading and writing memory itself. Only offsets within the bounds of /dev/mem are allowed.

Kernel virtual memory is accessed through the interface /dev/kmem in the same manner as /dev/mem. Only kernel virtual addresses that are currently mapped to memory are allowed.

On the VAX, the I/O space base address is 20000000(16). On all VAX'en the per-process data size for the current process is UPAGES long and ends at the virtual address 80000000(16).

Writeability of these devices is controlled by the system securelevel(7).



The /dev/mem and /dev/kmem files appeared in Version 6 AT&T UNIX.

July 6, 2011 OpenBSD-5.1